circuit design help: momentary switch activates/cancels electronic switch

Do you particularly want to use that switch or would you be prepared to swap it for a push-on/push-off momentary action one?

Ken

Will in the end, I need a circuit to do this. But I do want to learn. What I asked for is actually only part of the functionality, but I see it as a building block to start with and was hoping I might figure the rest out on my own.

Well a push-on push-off switch isn't really momentary. It feels like a momentary switch, but doesn't function like one. I have to use a momentary switch, no option because or existing hardware.

Well a push-on push-off switch isn't really momentary. It feels like a momentary switch, but doesn't function like one. I have to use a momentary switch, no option because of existing hardware.

There are a number of ways to do this. Do you want to learn, or are you just interested in having a circuit that will do it?

Ed

See "TogggleFlopAncient.pdf" on the S.E.D/Schematics page of my website.

...Jim Thompson

This should do it.

There are many circuits for a 'toggle' or flip-flop, but that's the simplest/cheapest I know of.

Did you simulate that?

"matthewuw" wrote in news:1129097288.402163.260420 @o13g2000cwo.googlegroups.com:

I've tried this and it works. Simple and cheap. Sub in a 12vdc supply and a

You can use a miniature SCR bistable: View in a fixed-width font such as Courier.

. . 12V . | . +--------------+--+----+--------------+-----+ . | | | | | | . | +-------------|--------------------------+ . | | | | | | | | . | | | | | +-----+ | | . [10M] [1K] | [1K] | | | | | . | | | | | | -|-----|-----|--- . | | | | | | | | | | | . | | | | | | | \\ COM NC | . | 0.0022 | | | |< - | / | . +---||---|--------+--| ^ | \\ | . | | | |\\ | | / | . | | | 2N2907| | | | NO | . | | | | | -|------------|-- . | | [100K] [3.3K] | | | . | | | | +-----+ | . | | | | | | . | +-----+--||---|--------------+ | . | | 100U 16V | | | . | | non- | | | . | | polar | | | . | | | | | . | | | | | . o | SCR1 | SCR2 | | . -| SW --- | --- | . o \\ /-+-[1K]-||-[1K]-+--\\ / LAMP . | --- | | | --- | . | NTE5400| | | | | NTE5400 | . | | | | | | | . | |[10K] [3.3K] [10K] | | . | | | | | | | . | | | | | | | . +--------+--+----------+----------+---+------------+ . | . --- . /// .

Should be: View in a fixed-width font such as Courier.

. . 12V . | . +--------------+--+----+--------------+-----+ . | | | | | | . | +-------------|--------------------------+ . | | | | | | | | . | | | | | +-----+ | | . [10M] [1K] | [1K] | | | | | . | | | | | | -|-----|-----|--- . | | | | | | | | | | | . | | | | | | | \\ COM NC | . | 0.0022 | | | |< - | / | . +---||---|--------+--| ^ | \\ | . | | | |\\ | | / | . | | | 2N2907| | | | NO | . | | | | | -|------------|-- . | | [100K] [3.3K] | | | . | | | | +-----+ | . | | | | | | . [470] +-----+--||---|--------------+ | . | | 100U 16V | | | . | | non- | | | . | | polar | | | . | | | | | . | | | | | . o | SCR1 | SCR2 | | . -| SW --- | --- | . o \\ /-+-[1K]-||-[1K]-+--\\ / LAMP . | --- | | | --- | . | NTE5400| | | | | NTE5400 | . | | | | | | | . | |[10K] [3.3K] [10K] | | . | | | | | | | . | | | | | | | . +--------+--+----------+----------+---+------------+ . | . --- . /// .

No, but maybe I'll have a crack at it when I get some time. Meanwhile, I've put together this scan from my original source: "Elektor 302 Circuits", ~1985

And I'm pretty sure I breadboarded it successfully a decade or two ago.

Okay, thanks for all the replies. Sorry to change things up on you...but like I said early on, this is a learning experience for me. It has occured to me that I don't want to worry about contact bounce and that in reality, this will fit my application much better if there are 2 momentary switches. pressing one of them turns the system on and pressing the other turns the system off. i can probably adapt this setup somehow from some of the provided circuits, so I will look into it. this might actually simplify the circuit too i would think. THANKS!

Here is a less parts intensive version of the same thing, consumes about

. . 12V . | . +-------------+-----+--------+-----+ . | | | | | . | o | | | . | -| SW | | | . | o | +----+ | . | | | | | | . | +------+ | | -|-----|--------- . | | | | | | | | | . | [10M] === | | | \\ COM | . | | 0.022U | - | / | . | -+- | | ^ | \\ | . | /// | | | | / | . | | [1.5K]| | | NO | . | [820] | | -|------------|-- . [100K] | | | | | . | | | +----+ | . | | | | | . +--------+--------||---|-----+--------+ | . | | 10U 16V | | | . | | non- | | | . | | polar | | | . [100K] | | | | . | | | | | . | SCR1| | SCR2 | | . | --- | --- | . | \\ /-+-[1K]-||-[1K]-+--\\ / LAMP . | --- | | | --- | . | NTE5400| | | | | NTE5400 | . | 2N5060 | | | | | 2N5060 | . | |[10K] [270] [10K] | | . | | | | | | | . | | | | | | | . +--------+--+----------+----------+---+------------+ . | . --- . /// .

Thanks- I think I recall that article now, clever.

A little before my time, but those were the days...toggle on release.

Ken Moffett wrote in news:Xns96EE4ED95F5AEqwerty@24.94.170.94:

I looked back at the circuit again and noted something they had left out. The relay in their circuit was a 12vdc for the 24v supply. So for a 12v supply you would choose a 5vdc or 6vdc DPDT relay. The resistance of R1, R2, and relay's coil would all be approximately equal.

How much simpler can you get than the circuits posted? Have you tried any of them yet?

Hey, how about an even simpler approach: a single toggle switch? No buttons, no electronics. AC or DC power supply in at one side, and out of the other to whatever you want to control. Its explanation is as follows: when you switch it one way, the circuit is powered on. When you switch it the other way, the circuit is powered off again. Very reliable, parts easily obtained. What's more, it has another advantage over a button-based approach: the status of the circuit is always visibly obvious (providing the two switch positions have been marked accordingly, e.g. 'On' and 'Off' or whatever.) This advantage over buttons applies even if the load has failed somehow (lamp filament burned out, motor stalled, etc).

--- This is the standard way to do it: (View in a fixed-pitch font like Courier)

S1 is a Single-Pole Single-Throw Normally Open (FORM 'A') momentary switch which can handle the relay coil current, S2 is a Single-Pole Single-Throw Normally Closed (FORM 'B') momentary switch which can handle the relay current, and the relay is a DPSTNO or a DPDT relay. One set of contacts is used to latch the relay in the energized position when S1 is pressed, and the other set is used for external purposes.

When S1 is pressed, current flows through the relay coil, which attracts the armature of K1A to the normally-closed contact. When they touch, another path to +V will be established for the coil, latching the relay. S1 can then be released and the relay will remain energized.

When S2 is pressed, the path to ground for the current will be broken, the magnetic field around the relay coil will collapse, and the contacts will spring back to their non-energized state.

-- John Fields Professional Circuit Designer